FI3261687T3 - Implant for covering maxillary bone defects and method for producing the same - Google Patents

Claims (9)

1 EP3 261 687 IMPLANT FOR COVERING MAXILLARY BONE DEFECTS AND METHOD FOR PRODUCING THE SAME Description Field of the invention The invention relates to a bioresorbable implant for covering bone defects in the jaw region and to a method for producing the same.

In particular, the invention relates to an implant which is placed over a defect site filled with a bone replacement material and over which the soft tissue is then closed.

Background of the invention

Implants for covering bone defects in the jaw region are known.

There are both bioresorbable implants, which slowly dissolve after implantation, and implants that either remain in the body or have to be removed again after a certain period of time.

A general overview of known implants for covering bone defects is provided by the article “Mechanisms of Guided Bone Regeneration: A Review, the Open

Dentistry Journal, 2014, 8, pp. 56-65” by Liu et al.

Thus, there are non-resorbable PTFE membranes.

They can be implanted easily but must be explanted.

Furthermore, there are in particular collagen membranes as resorbable material.

They have the advantage that they do not have to be explanted, which is however associated with the disadvantage that they are not particularly tight, so that there is a risk that soft tissue grows into the filled bone defect site or bone material exits from the defect site.

Document JP 2010 082146 shows a porous membrane which is provided with a magnesium layer as a support layer.

Documents US 2013/0304134 A1 and DE 10

2006011348 A1 show biodegradable magnesium implants provided with a passivated protective layer.

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IAN JOHNSON ET AL: "A Study on Factors Affecting the Degradation of Magnesium and a Magnesium-Yttrium Alloy for Biomedical Applications," PLOS ONE, vol. 8, No. 6, June 24, 2013 (2013-06-14), page 65603, XP055332048, DOI: 10.1371/journal.pone.0065603 is a study on the degradation properties of magnesium and of various magnesium alloys.

Document JP 2011 136967 A shows an implant designed as a lattice made of a magnesium alloy.

Object of the invention In contrast, the invention is based on the object of reducing the mentioned disadvantages of the prior art.

It is in particular an object of the invention to provide a bioresorbable implant that can be implanted easily and reliably separates soft tissue from bone material, in particular from bone replacement material, in the initial phase after implantation.

Summary of the invention

The object of the invention is already achieved by an implant for covering bone defects in the jaw region according to claim 1. Preferred embodiments and developments of the invention can be found in the subject matter of the dependent claims.

The invention relates to an implant for covering bone defects in the jaw region according to the claims, which implant consists of a magnesium film.

A magnesium film is understood to mean a film made of magnesium or of a magnesium alloy predominantly consisting of magnesium, i.e., at more than 50 % (% specifications are always % by weight unless otherwise indicated). Surprisingly, it has been shown that such a magnesium film leads to clean separation of the soft tissue from the defect site, which is in particular filled with a bone replacement material, such as, in particular, also homologous or autologous bone grafts.

3 EP3 261 687 The bioresorbable properties of magnesium are known as such.

However, it is quite surprising that even a film in the jaw region withstands a corrosive attack so long that the growth of natural bone tissue into the defect site is completed, such that soft tissue does not grow in until the implant is at least partially degraded.

The invention is suitable for all types of treatment of bone defects in the jaw region, in particular also of sinus lift corrections.

In particular, calcium phosphate- or hydroxylapatite-containing materials are used as bone replacement material.

They may be both artificial and natural materials, in particular also materials that are produced from donor bones of, for example, human or porcine origin.

The bone replacement material can be implanted both as a granulate and as an adapted molded body that approximates the contour of the defect site at least in sections.

The implant is preferably dimensionally stable.

This means that, for example, a curved implant does not change shape due to its own weight force.

For this purpose, a magnesium film with a thickness of between 70 and 200 um is used according to the invention.

The implant is preferably curved.

Thus, it can be placed onto the defect site and, in the most favorable case, even be clamped on the jaw ridge.

In particular, a radius of curvature of 0,5 to 10 cm, preferably 0,7 to 1,5 cm, is provided at least in sections.

It has been found that a magnesium film of the mentioned thickness can also, in particular, be bent at an angle > 30°. The angle is defined by the angle the tangents of the ends of the implant assume to one another.

In particular, it is provided that the sides of the implant are parallel and opposite one another or even assume an angle of more than 180° in order to fix, in particular to clamp, the implant.

In a development of the invention, the implant has at least one recess for a tooth.

4 EP3 261 687 The implant is preferably recessed at a front and/or rear end such that the adjacent sides partially surround the tooth. As a result, implantation is facilitated on the one hand, and the risk of ingrowth of soft tissue is further reduced. The implant preferably has a size of 0,5 to 25 cm?. If a recess for a tooth is provided, the recess preferably occupies an area of more than 0,25 cm?. In a development of the invention, the implant comprises a coated and/or etched surface. It has been found that in particular an implant immersed in an acid has improved properties with regard to possible bending radii and with regard to corrosion properties. The implant preferably also has a smooth surface with a mean roughness value Ra of below 0,08, preferably below 0,03 and particularly preferably below 0,02 um. Such a smooth surface can in particular be achieved by an acid treatment, for example with nitric acid. In particular, etching and/or passivation is provided as a surface treatment. It has proven to be particularly suitable to for a pre-cleaned implant, in particular an implant pre-cleaned with acid, to be immersed in hydrofluoric acid for at least 10 minutes, whereby, as a result of agitated immersion, a protective layer of magnesium fluoride is formed. The passivated surface, in particular the magnesium fluoride layer, preferably has a thickness of less than 5, particularly preferably of less than 2 um. In particular, it is provided to produce a layer whose thickness is between 0,2 and 2 um, preferably between 0,7 and 1,5 um. A well-interlocked, preferably pore-free, scratch-resistant layer is thus formed, which is not prone to tearing even with narrow bending radii. According to the invention, the film has no openings at least in a central region,

i.e., in particular the region arranged directly above the defect site. This ensures tight closing of the defect.

EP3 261 687

In a development of the invention, the implant is structured and/or perforated in sections, in particular along a peripheral area thereof.

In particular via a perforation, for example in the form of a lattice structure, or via structuring, in particular pleating, the bending of the implant can be facilitated and/or its

5 adhesion to the adjacent tissue can be improved.

The implant preferably consists of pure magnesium (degree of purity above 99 %) or a magnesium alloy.

The latter can comprise 1 to 6 % yttrium, 0,5 to 3 % zinc, 0,1 to 2 % calcium, and/or 0,6 to 1,5 % manganese.

On the other hand, the magnesium film preferably has less than 500 ppm of iron,

copper, and/or nickel.

The invention also relates to a kit for covering bone defects in the jaw region, which kit comprises an implant as described above and pins for fixing the implant in the jaw.

Pins within the meaning of the invention are understood to mean, in particular, pins, nails, or screws.

The pins also preferably consist of magnesium or a magnesium alloy.

As is provided in a development of the invention, the implant can have holes through which the pins are guided.

However, it is also conceivable to introduce the fastening hole with the pin itself, in particular if the pin has a tip.

The implant according to the invention can be produced as follows.

First, a magnesium film is provided.

The magnesium film is shortened to the length of a site to be covered, and the magnesium film is bent.

The bending of the magnesium film is preferably carried out by means of a mold or by means of a bending machine, since the risk of kinks and edges is thus reduced.

In order to shorten the implant to the desired length and/or to introduce recesses for a tooth, for example, the implant can be cut or punched, for example.

For forming a layer, the magnesium film is preferably treated with hydrofluoric acid, in particular over a period of more than 10, preferably more than 12 hours, and in particular with a more than 30 % hydrofluoric acid.

6 EP3 261 687 The implant can be used for a method for cosmetic and/or surgical jaw reconstruction, wherein the implant described above is placed over a defect site, which is filled in particular with a bone replacement material, and the soft tissue is closed over the defect site, in particular by sewing.

It has been shown that it is possible with the magnesium film according to the invention in a simple way to provide a bioresorbable implant that largely prevents ingrowth of soft tissue during the formation of natural bone material.

The implant does not need to be removed but degrades.

Surprisingly, in spite of the relatively large surface area of the film used, bubble-forming gas developments do not occur to an undesirably high extent.

After the formation of natural bone tissue, a pivot tooth implant can then be implanted into the former defect site, for example.

It is possible to already implant the pivot tooth implant before the magnesium film has degraded.

The implant according to the invention is in particular suitable for the following application possibilities: On the one hand, implants designed as magnesium film can be used for the treatment of injuries to the Schneiderian membrane.

The Schneiderian membrane separates the jawbone from the jaw cavity.

In the event of injury thereof, there is extreme risk of infection.

It has been found that such a defect site can be closed by implanting a thin magnesium film.

In this case, the magnesium seems to also have an anti- inflammatory effect, probably to the increase in the pH value, and furthermore accelerates the formation of natural bone tissue, for example when bone filler material is implanted.

A further possibility for use is the avoidance of wound dehiscences, which frequently occur with conventional membranes, for example with PTFE membranes.

These materials must also be removed in a further surgery.

It has been found that suture line dehiscences over a magnesium film spontaneously result in complete wound closure.

7 EP3 261 687 Defects of up to 10 mm can thus be tolerated without any infection occurring. Astonishingly, the film corrodes quite slowly and remains mechanically stable over a long period of time. Furthermore, defect sites in the jaw ridge can be eliminated. In particular, a magnesium film under a periosteal flap can by itself bring about regeneration of the cortical wall. The treatment for regeneration of the cortical wall is possible in any region thereof, in particular of the lateral cortical wall. Under defect sites, such as the exposed region of a pin implant, a cortical wall forms around the defect site. Finally, magnesium films can also be used preventively for initial postsurgical infection protection. Furthermore, due to the dimensional stability, the implants according to the invention are suitable for forming complex three-dimensional bone regenerates. In this case, the filler material is introduced into the defect site below the magnesium film. Due to the three-dimensional, dimensionally stable free-form surface, the magnesium film ensures this shape up to osseous consolidation and then dissolves completely. Brief description of the drawings The subject matter of the invention is explained in more detail below with reference to exemplary embodiments and based on the drawings of Figs. 1 to 8.

Fig. 1 shows an exemplary embodiment of an implant 1 for covering bone defects in the jaw region.

Fig. 2 shows the implant in a side view.

Fig. 3 shows a further embodiment of an implant. Figs. 4 to 6 show scanning electron micrographs of an implant.

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Fig. 7 schematically shows the use of an implant according to the invention for preventing or treating injuries to the Schneiderian membrane.

Fig. 8 schematically shows the use of an implant according to the invention for so-called “lateral augmentation” (jawbone reconstruction). Detailed description of the drawings

Fig. 1 shows a first exemplary embodiment of an implant for covering bone defects in the jaw region. In this exemplary embodiment, the implant 1 consists of a magnesium film 2 which is 50 to 150 um thick and consists in particular of a magnesium alloy. The implant 1 has rounded corners and, in this exemplary embodiment, has two recesses 3 which are provided for an adjacent tooth. The implant is thus designed in particular to cover a defect site in the jaw, in which a tooth or several teeth are missing.

Fig. 2 shows the implant 1, shown in Fig. 1, in a side view, specifically in a plan view of the recess (3 in Fig. 1). It can be seen that the implant is curved. In this exemplary embodiment, the ends of the implant are located almost opposite one another, so that the implant can be fixed, in particular clamped or clipped, on a jaw ridge.

Fig. 3 shows a development of an implant 1. The implant 1 has, on the one hand, holes 5 which serve to insert sutures, pins, screws, or nails. Furthermore, the implant 1 in this exemplary embodiment comprises, along a peripheral area thereof, a net-like region 7, i.e., an region which has recesses. These recesses can serve for easier bending or improved adhesion to the tissue. A structured region 6 is also shown. This region can in particular be designed as a pleating and serves to adapt the implant 1 to the jawbone.

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Fig. 4 shows a scanning electron micrograph of the surface of an implant, with which a magnesium film was provided with a magnesium fluoride coating by means of immersion in hydrofluoric acid. This results in a smooth, scratch-resistant layer that is approximately 1 um thin andalso allows narrower bending radii.

Fig. 5 likewise shows a scanning electron micrograph of a section of the film, in which the magnesium fluoride layer can already be clearly seen.

Fig. 6 shows a detail representation of Fig.

5. The thin magnesium fluoride layer 9 formed on the magnesium layer 8 can be seen. It can be clearly seen that the magnesium fluoride layer 9 is interconnected well with the underlying magnesium layer, which presumably inter alia explains the good adhesion of the layer.

Fig. 7 shows a schematic representation of a first possible use of the implant according to the invention. The implant according to the invention designed as a magnesium film can be used for treating injured Schneiderian membranes. In particular when pin implants 14 are implanted, as is shown here, which serve to receive a dental implant, injury to the Schneiderian membrane 12, which separates the jawbone 13 from the jaw cavity, may occur. In many cases, as is shown here, an intermediate space between the jawbone 13 and the Schneiderian membrane 12 is filled with a bone replacement material, in particular a calcium phosphate granulate, in order to increase the thickness of the formed jawbone in such a way that the implant 14 can be implanted. The injury to the Schneiderian membrane 12 is accompanied by an extremely high risk of infection. If such an injury is noticed during the surgical intervention, the intervention is generally discontinued and another attempt at implanting the pin implant 14 is made only after a healing phase of several months.

10 EP3 261 687 It has been shown that this can be avoided by using an implant according to the invention in the form of a magnesium film which closes the Schneiderian membrane 12. Thus, for example, in the case of a defect, the magnesium film can be implanted either through the bores of the pin implants 14 or through a lateral opening of the jaw ridge 13. It is understood that the magnesium film can be rolled up beforehand, for example, if it is implanted through the bores for the pin implants. The Schneiderian membrane 12 is closed again by the magnesium film. Astonishingly, a thin magnesium film of at least 50 um already ensures sufficient closure without being degraded within a very short period of time, as is actually to be expected. The magnesium film can thus enable the intervention to be continued immediately and also offers the advantage that the magnesium film, in particular if it is sufficiently thick, provides a good counterforce for the implanted bone material. The growth of natural bone tissue is likewise promoted by the magnesium film. It is understood that the magnesium film can however also be implanted preventively, without injury to the Schneiderian membrane.

Fig. 8 schematically shows the use of an implant 1 according to the invention for the three-dimensional reconstruction of defect sites in the jawbone. A jawbone 10, which has a defect site 11, is covered with a bent implant 1 consisting of a magnesium film. The implant 1 forms a three-dimensional free-form surface. As can be seen in the right-hand illustration, the forming bone tissue of the jaw ridge 10 follows this free-form surface and forms a rounded jaw ridge which comes close to the natural shape. This approximation is generally better than when using implanted bone blocks of donor material. By means of the invention, a resorbable implant for covering bone defects in the jaw region could be provided in a simple manner.

11 EP3 261 687 List of reference signs 1 Implant 2 Magnesium film 3 Recess 4 Corner 5 Hole 6 Structured region 7 Net-like region 8 Magnesium layer 9 Magnesium fluoride layer 10 Jaw ridge 11 Defect site 12 Schneiderian membrane 13 Jawbone 14 Pin implant 15 Filler material